important methodological differences between the navy...

Important Improvements of the Duke 2015 Density Models Over the 2007 Navy NODEs Models for the U.S. Atlantic

Jason Roberts and Pat Halpin, Duke Marine Geospatial Ecology Lab

Updated 23 February 2016

Navy OPAREA Density Estimates (NODEs) models

• Funded by the Navy to support development of the Atlantic Fleet Active Sonar Training (AFAST) EIS (finalized January 2009)

• Developed by Geo-Marine, Inc.

• Utilized NOAA NEFSC and SEFSC surveys spanning 1998-2005

• Final report issued in 2007

• Not submitted to a peer-reviewed scientific journal

• Reused for the Navy’s Atlantic Fleet Training and Testing (AFTT) Phase II EIS (finalized November 2013)

– AFAST was AFTT Phase I

Duke 2015 density models (a.k.a. CetMap)

• Initial funding from NASA for certain methodological work

• Main funding from the Navy to support the AFTT Phase III EIS

– Specifically intended to replace NODEs with models built with additional data and updated methodology

• Developed at Duke in consultation with NOAA and others

• Utilized surveys from five institutions

• Models finalized in January 2015

• Peer-reviewed paper accepted for publication in February 2016

– http://dx.doi.org/10.1038/srep22615

http://dx.doi.org/10.1038/srep22615

Important improvements of Duke models over NODEs

1. Utilized a more flexible study area design

2. Incorporated much more survey data

3. Modeled more cetacean species

4. Modeled more species with density surface models (DSMs)

5. Used species-specific seasons

6. Predicted more species at high temporal resolution

7. Utilized more detection functions, when data allowed

8. Controlled for the influence of sea state, glare, group size and other factors on detection probability

9. Controlled for availability and perception bias

10. Considered many more environmental covariates in DSMs

NODEs study areasSoutheast NODE study area Northeast NODE study area

• NODEs effectively assumed that species are distributed mainly in one area or the other

• Species do not conform to these patterns• For example, humpbacks and

harbor porpoises occur south of Cape May in winter

• For many species, Cape Hatteras is a more appropriate ecoregional boundary than Cape May

Duke study areaHumpback whale – summer Right whale – spring Beaked whales – year round

• We split the study area into taxon-specific seasonal model sub-regions according to the known ecology of each taxon

• We combined sub-region predictions into a full-region raster, for convenience

• We incorporated surveys spanning 1992-2014; NODEs spanned 1992-2005

• As a result, in the Atlantic we utilized 1276% more aerial and 58% more shipboard survey hours than NODEs

Duke Duke

NODEsNODEs

Surveys used in Duke models

NODEs used a subset of the surveys boxed in red

Northest NODE Southeast NODE

Duke

NODEs

15 total6 total

11 total

• We modeled 15 cetacean taxa with density surface models

– These are models in which density was modeled according to environmental covariates such as depth, sea surface temperature, and so on

• The northeast NODE modeled 6 taxa

• The southeast NODE modeled 11 taxa

Seasonality in the NODEs models

NODEs used the same seasonal definitions for all species:

Evidence suggests different species migrate at different times

(This is from the Northeast NODE report)

Right and sei whale arrival in the Great South Channel

• Right whales begin arriving in the Great South Channel in March

• Sei whales do not arrive in large numbers until April

North Atlantic right whales Sei whales

Arrival starts Arrival starts

Seasonality in the Duke density models

• Philosophy: define seasons on per-species basis, based on ecology

• We split data into separate seasonal models, on month boundaries, when:• Literature suggested species exhibits seasonality in which its relationship to the

environment is expected to be different during different seasons (e.g. baleen whales feeding vs. breeding/calving), and:

• We had sufficient sightings to model at least one of the seasons effectively, and:

• The spatial pattern in the sightings resembled the expectation

• When any condition was false, we fit a “year-round” model

7

Duke

NODEs

• We predicted monthly maps for 11 taxa

• The northeast NODE predicted seasonal maps for 6 taxa and monthly maps for 1 taxon (right whales)

• The southeast NODE predicted seasonal maps for 4 taxa and monthly maps for 1 taxon (right whales)

Scaling detection functions based on the modeled taxon’s rarity

* Additional surveys from other regions used in detection functions only (not in the EC or GOM spatial models)

Bottlenose dolphin aerial detection hierarchy5630 sightings, 17 detection functions

Risso’s dolphin aerial detection hierarchy368 sightings, 7 detection functions

Example: dolphins on shipboard cruises that used naked eyes

Availability bias: not available to be seen (diving)

Perception bias: hard to see (e.g. the seal below)

NODEs did not address these biases for many species

(This is from the Northeast NODE report)

• By not addressing these biases, NODEs underestimated abundance, especially for long-diving animals such as beaked whales– They noted this in their report, as you can see above

• Both the NOAA SARs for the Atlantic and the Duke models do address these biases

Type Covariates Resolution Time range Description

Ph

ysi

og

rap

hic

Depth,

Slope

30 arc sec Seafloor depth and slope, derived from SRTM30-PLUS

global bathymetry20

DistToShore,

DistTo125m,

DistTo300m,

DistTo1500m

30 arc sec Distance to the closest shoreline, excluding Bermuda and

Sable Island, and various ecologically-relevant isobaths20

DistToCanyon,

DistToCanyon

OrSeamount

30 arc sec Distance to the closest submarine canyon, and to the closest

canyon or seamount21

SS

T &

Win

ds SST,

DistToFront

0.2°, daily 1991-2014 Foundation sea surface temperature (SST), from GHRSST

Level 4 CMC SST22, and distance to the closest SST front

identified with the Canny edge detection algorithm23

WindSpeed 0.25°, daily 1991-2014 30-day running mean of NOAA NCDC 1/4° Blended Sea

Winds24

Cu

rren

ts

TKE,

EKE

0.25°, daily 1993-2013 Total kinetic energy (TKE) and eddy kinetic energy (EKE),

from Aviso 1/4° DT-MADT geostrophic currents

DistToEddy,

DistToAEddy,

DistToCEddy

0.25°, weekly 1993-2013 Distance to the ring of the closest geostrophic eddy having

any (DistToEddy), anticyclonic (DistToAEddy), or cyclonic

(DistToCEddy) polarity, from Aviso 1/4° DT-MADT using a

revision of the Chelton et al. algorithm25; we tested eddies at

least 9, 4, and 0 weeks old

Bio

log

ical

Chl 9 km, daily 1997-2014 GSM merged SeaWiFS/Aqua/MERIS/VIIRS chlorophyll

(Chl) a concentration26, smoothed with a 3D Gaussian

smoother to reduce data loss to < 10%

VGPM,

CumVGPM45,

CumVGPM90

9 km, 8 days 1997-2014 Net primary production (mg C m-2 day-1) derived from

SeaWiFS and Aqua using the Vertically Generalized

Production Model (VPGM)27; we tested the original 8 day

estimates as well as 45 and 90 day running accumulations

PkPP,

PkPB

0.25°, weekly 1997-2013 Zooplankton production (PkPP; g m-2 day-1) and biomass

(PkPB; g m-2) from the SEAPODYM ocean model28

EpiMnkPP,

EpiMnkPB

0.25°, weekly 1997-2013 Epipelagic micronekton production (EpiMnkPP; g m-2 day-1)

and biomass (EpiMnkPB; g m-2) from the SEAPODYM

model28

Covariates used in Duke models• Each model only considered the

covariates that were appropriate for the modeled region and known ecology of the taxon– For example, we did not use distance to eddy

covariates for on-shelf sub-regional models, because geostrophic eddies rapidly decoherewhen they reach the shelf break

– We tried WindSpeed in the right whale calving area model, based on a suggestion from the literature (Good 2008) (it was not selected). We did not use it in any other models.

• NODEs used covariates marked with *

**

*

*

*

*

In conclusion

• The NODEs models utilize 10 year old data and methodology

• The Duke 2015 models incorporated many additional datasets and methodological improvements

• The Navy, NOAA OPR, NROC, and MARCO have adopted the Duke models as their baseline cetacean density maps

• The NODEs models should be considered obsolete and no longer be used

important methodological differences between the navy...

Documents